Hollow cavitied bodies such as rigid hollow panel structures and method of making the same



July 13, 1948. D. GONDA 2,445,290

' HOLLOW CAVI'IIED BODIES SUCH AS RIGID HOLLOW PANEL STRUCTURES AND METHOD OF MAKING THE SAME Original Filed Dec. 22, 1941 4 Sheets-Sheet 1 4 Ur 1 1f J 4 Z} 1 H763 5 2 2 F JP J JV J I: g S 17 mP sire Gw-nda D. GONDA July 13, 1948.

2,445,290 HOLLOW CAVITIED BODIES SUCH AS RIGID HOLLOW PANEL STRUCTURES AND METHOD OF MAKING THE SAME Original Filed Dec. 22, 1941 4 Sheets-Sheet 2 id W I Desire Game/d lnve'n'far I A n ne /s F/GIO.

ONDA LLOW CAVIIIED BODIES SUCH AS RIGID HOLLOW PANEL STRUCTURES AND METHOD OF MAKING THE SAME Original Filed Dec. 22, 1941 July 13, 1948.

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4 Sheets-Sheet 3 v Desire nds by WiM July 13, 1948. GONDA 2,445,290

HOLLOW CAVITIED BODIES SUCH AS RIGID HOLLOW PANEL STRUCTURES AND METHOD OF MAKING THE SAME Original Filed Dec. 22, 1941 4 Sheets-Sheet 4 F/GZO INVENTOR. 1 851 16. Gouda BY Patented July '13,, 1948 noLLow cAvrrIEn B onrss sUon As mom I HOLLOW PANEL STRUCTURES AND METH- OD OF MAKING'THE SAME Desir Gonda, London, England,

assignor to H010- plast, Limited, New Hythe, near Maidstone,

England, a British corporation Original application December 22, 1941, Serial No. 424,090. Divided and this application February 23, 1945, Serial No. 579,429

10 Claims.

This application is a division of my co-pending application Serial No. 424,090, filed December 22, 1941, now abandoned, and the invention covered herein relates to methods of producing rigid hollow panel structures. More particularly it relates to methods of manufacturing such structures from fibrous materials that contain or are impregnated with thermo-setting resins, such as phenol formaldehyde, urea-formaldehyde or cresol-formaldehyde resins, the fibrous materials utilized preferably being in the form of laminae of fibrous sheets, such as paper. The structures produced consist of at least two sheets or sheetlike elements positioned one above the other in spaced relationship throughout their area, and joined together by web members that are positioned inspaced relationship to one another and extend transversely between the sheets. These panel structures (or hollow bodies as they are sometimes termed herein), when complete, after suitable heating and pressing operations, constitute integral reinforced units, homogeneous to the eye, the material being compressed and densified and all portions firmly bonded together. Such structures may be manufactured in large units, which have excellent mechanical and other useful properties, making them'well adapted for various structural purposes. I

Hollow bodies or panels as made according to the invention may find very extensive and varied employment in industry, but their suitability for use in the construction of bulkheads and linings in ships may be mentioned as one instance in which they may be employed with very considerable advantage. At the present time the bulkheads and linings'employed extensively in the construction of ships are formed of plywood which is, among other things, combustible, water absorbent, liable to deterioration in damp or wet conditions, and to attack by insects, and are affected by acids. Hollow bodies according to this invention do not suffer from these disabilities; some of the advantages derived from using them in the construction of ships will therefore be obvious.

An additional object of the invention is the provision of an improved rigid hollow panel structure as hereinafter described.

An object of this invention is'the provision of efficient and improved methods for the production of such panel structures, which may be used with advantage in place of present day materials in the construction of ships, buildings and other structures. Other objects comprise the provision of improved steps and combinations thereof which are particularly designed to make large scale manufacturing operations effective, and to ensure that the product shall erties required of it as a constructional unit.

In accordance with the invention, the spaced sheets of the structure, which are joined together by the webs, are formed of apluraiity' of laminae of fibrous sheet material which are bonded together by the thermo-setting resin contained therein, during the process. The'webs also are preferably formed of laminated fibrous sheets, such as paper or fabric, containing the resin, and they preferably are of quadrilateral, e. g. rectangular tube construction or ofgirder construction to provide lateral fianges which become integrally united with the spaced sheets of the panel, when the resin has set.

In the process, the said spaced sheets are positioned on opposite sides of the web forming membars, which are arranged to extend side by side across one dimension of the sheets with cavitydefining members, such as mandrels, therebetween,these mandrels being arranged to make close contact with all adjacent surfaces of the material which will be hardened to form the finished structure. The assembly is simultaneously subjected to heat and pressure, the pressure being applied in directions both parallel to the major surfaces or planes of the said sheets and transverse of the lengths of the transverse portions of the web members and also transversely of the major surfaces or planes of the said sheets. As a result, the resin is softened and caused to flow in and through all parts of the fibrous structure, the material is compressed and densified and, when the resin has set, all parts are simultaneously bonded together into an intergral rigid structure which is homogeneous in appearance, that is, to the unaided eye. Thereafter the mandrels are removed lengthwise.

In this process, certain practical difliculties have had to be overcome. The mandrels required must be able to withstand the pressure when the assembly is compressed, they must in most cases be good conductors of heat, and it must be possible to withdraw them lengthwise after the heating and pressing, so that they must have surfaces which are made as frictionless as possible, as by being smooth and polished, When heat is applied from the heated platens of the press, the mandrels should be heated to a temperature sufficiently high to prevent crystallization of the resin on the surfaces of the structure in contact with the mandrels which, as is well known, occurs when the resin sets against a cold surhave the mechanical propface. Also, the difference in temperature between the mandrels and the surrounding formed structure should be as small as possible, to reduce friction when the mandrels are withdrawn and the entire assembly, including the mandrels, should be such as to aid in the conduction of heat to all portions of the impregnated fibrous material, since all portions of the web members must be thoroughly cured. Therefore in practice metal mandrels are usually required, and the assembly for a panel unit of a size suitable for use in ship construction, for example, including the necessary number of mandrels, is very heavy.

When such an assembly, built upon bottom sheets of flexible material, such as paper, is to be transferred to the press the difficulty arises of maintaining all parts in their proper positions during the transfer. This may be accomplished by imparting rigidity to the assembly, by providing it with higid heat-conducting top and bottom plates and preferably by clamping all of the web-forming members and mandrels together in a frame which has removable side portions and means, whereby also necessary pressure is applied transverse to the transversely-extending portions of the web members to compress and densify the same and to ensure the close contact between all parts of the same and the mandrels which aids in the most thorough conduction of heat to all parts. It should also be remarked that, the structure being hardened around the mandrels under considerable pressure, the problem of withdrawing them afterwards, in the case of large scale work, was believed to be one which would present great difliculty, but it was found that, with the methods and precautions indicated herein, they can be extracted from the opposite ends of the structure by suitable power without injury to the structure.

In the preferred method the web forming members are formed from unbroken continuous strip material rolled into a plurality of convolutions or folded upon itself to provide laminae which extend in continuous circuit without interruption throughout the strut and laterally extending portions of each member so that, the fibres extending in arch formation from the vertical into the horizontal portions of the member, the best conditions for obtaining strength at the Junction of the upright or strut and laterally extending portions will be obtained.

In the appended drawings, a number of alternative forms of construction and methods for producing the same are illustrated, from all of which some of the advantages of the invention are obtained, preferred forms and methods, however, being as above indicated.

In the drawings:

Figure 1 is a perspective view of a portion of a typical hollow body or panel structure constructed in accordance with this invention.

Figure 2 is an end elevational view of a panel structure such as that shown in Figure 1, but which is provided with a facing material on its upper and lower surfaces.

Figure 3 is an end-elevational view of a combination of a hollow body or panel structure such as that shown in Figure 1 in which the top surface of the body is molded with an ornamental surface.

Figure 4 is a partial cross-sectional view illustrating diagrammatically apparatus employed in manufacturing one form of a panel structure in accordance with this invention.

Figure 5 is a plan view, with the top cover plate removed, of the apparatus illustrated in Figure 4.

Figure 6 is a cross-sectional view taken along line 6-4 of Figure 5.

Figure '7 is an elevational view similar to Figure 5 but illustrates the manner in which the apparatus is disassembled.

Figures 8, 9, 10 and 11 show diagrammatically various alternative methods for producing the webs of the hollow body.

Figure 12 is a fragmentary perspective view partially in elevation and partially in crosssection, illustrating a further modified method according to the invention of forming a rigid hollow body or panel structure.

Figure 13 is a. perspective elevational view showing a method of making the tubular members shown in Figure 12.

Figure 14' is a cross-sectional view of a tubular member made according to the method illustrated in Figure 13.

Figure 15 is an end elevational view showing a panel structure constructed with tubular members.

Figure 16 is a plan view, with the top cover plate removed, of apparatus forsproducing a panel section from the assembly of materials illustrated in Figure 15.

Figure 1'7 is an end view of a panel structure similar to Figure 15 but showing the tubular members as having a trapezium shape.

Figure 18 is an end view, partially in crosssection, of a further modified arrangement of a panel structure constructed in accordance with this invention.

Figure 19 is a perspective fragmentary view illustrating an apparatus for constructing the hollow body shown in Figure 18.

Figure 20 is an end-elevational view of a web forming member shaped in the form of an I.

Figure 21 is an end-elevational view of a tubular member from which the web member shown in Figure 20, may be constructed.

Figure 22 shows diagrammatically a front elevational view of an apparatus for converting the tubular member shown in Figure 21 to the I- shaped member shown in Figure 20.

Figure 23 shows diagrammatically a slide-elevational view of the apparatus illustrated in Figure 22.

Figure 24 shows diagrammatically a plan view of the apparatus illustrated in Figures 22 and 23 Figures 25, 26 and 27 show, respectively, a front elevational view, a side elevational view, and a plan view of a modified form of apparatus for converting the tubular member shown in Figure 21 into the I-shaped member shown in Figure 20.

Referring to the drawings, it will be seen that in Figure 1 there is shown a portion of a hollow body or reinforced panel structure, generally indicated by the reference numeral I, that is constructed in accordance with this invention. The hollow body or panel structure comprises a top sheet 2 and a parallel bottom sheet 3 that is spaced from and is connected to the top sheet 2 by the webs 4 extending transversely between the sheets 2 and 3. The webs l are in spaced relationship to one another, and preferably extend all in one direction continuously throughout the width or the length of the sheets 2 and 3. Between the web 4 and the sheets 2 and 3, chan nels or passages 5 are provided which extend in parallel relationship from one side to the other of the hollow body.

rials such as wood'in which the top ,of the fibrous rectangular so' that one or'more the parts of'the frame menslons of the the group i the same depth or thickness the example illustrated two cavity-defining memprovided.

' faces together so as to "form,

It will be understood thlt the panel structur either of them. t can be filled with a heat to resist thermal structure.

hollow body may have a decorative suri ace molded thereon. such as the the panel I.

One method of producing the hollow body or panel structure in accordance with this invention is'illustrated in Figures 4, 5, 6 and I.

The top and bottom sheets 2 and I, of the hollow body are formed from a plurality of laminae H of fibrous sheets, e. g. paper, which have been treated or impregnated with an uncured theme-setting resin, for example. phenol-formaldehyde, urea-formaldehyde or cresol-formaldehyde resin. The treatment may be effected in any convenient manner either during manufacture of the sheet material or subsequently to such manufacture, and the treatment may comprise complete impregnation of the'fibrous sheet or merely the coating or spraying of the sheet with the resin in solution. The treated fibrous sheets are preferably dried before being used, this dryirlg'being carried out in any convenient manner as with the aid of drying ovens. Suitable paper, having the fibres thereof extending in all direction'sin the plane of the paper, final product, when all parts are setting of the r therein, than fibrous matefibres are all more or less parallel.

One group of fibrous sheets II is placed upon a lower fiat metal cover plate orplaten l2 and sheets II (which are of shape in plan) is mounted a rectangular metal framell which is constructed sides is or are removable. It will'be seen, for example, by examining Figure 5, that either the side It or the side I! can be removed by removing the rew's It or ll holding together. The inside diframe I! when closed are rather less the overall length andbreadth of the gro p sheets II on which the frame is placed. Within the frame It, and on top of of'fibrous sheets II on the plate H, are arranged a n ber of removable cavity-defining members or mandrels as the frame It. In

bers lt'and I! of and ii of These cavity-defining members are so the frame I! as to leave, between adof the wedge-shaped ones, cavities I! to receive the material from which the webs of the hollow body are to be formed. cavities 22 are defined on one side by one of the wedgeshaped cavity-defining members 20 or I! and on the other side by one of the cavity-defining members It and I9.

-It will be seen from Figure 5 in disposed in iac'ent pairs particular that the wedge-shaped cavity-defining members it and 1' II are arranged in pairs with their tapered surcavity-defining members of rectangular prism 'form.

makes a stronger bonded by the formed as bars of metal of V The end together, divisible The next step inthe manufacture of the frame It fibrous treated'sheets ii, similar in form and size to the group placed below the frame, although the number of fibrous sheets employed at the top need not necessar ly be the same as the number of fibrous sheets ll used at the bottom of-the f Then on top of the upper fibrous sheets H is placed a top metal cover plate 14. The plates i2 and 24 are preferably rather greater in length and breadth than the frame 13. The whole assembly is now placed in a steam or electrically or otherwise suitably heated press, conveniently a hydraulic press, and subjected to heat and pressure of such a degree and for such a time as will insure the softening and flow of the thermo-setting resin of the assembly so as to insure the uniting of the various therr'no-setting resin containing parts of the assemblyfand then the setting and hardening of the thermo-setting resin with the consequent final uniting of the hitherto separate parts used in the manufacture. After the completion of the heating and pressing operation-the parts will have, in transverse crosssection'. the form approximately illustrated in Figure 6 of the drawings, and this assembly is taken from the pressing apparatus and when sufilciently cool the top plate 24 is removed, then the side ll of the frame II is remove after'first releasing the screws it, the's'ide of theifra me being drawn of! in the direction of the arrows A shown in Figure 7. The other three sides of the frame llxare'then removed bodily in the direc- B, thus exposing the edges of body. The cavity-defining members It. ll, 2! and 2| are then removed from the hollow body by moving them endwise. Figure '7 shows these members in the process of being removed. The tapered form of the cavity-defining members 2. and 2| assist the removal of these members from the hollow body.

The cavity-defining members ll,- IS, 2. and 2! preferably have highly polished surfaces-and-similarly the inner surfaces of the plates l2 and it may also be highly polished, although'where.it is required to give one or be and l of the hollow body a matt or other-nonpolished-plain surface. then the corresponding cover plate [2 or 24 would have an appropriately formed surface instead or a highly polished one. The said frame I! and cavity-defining elements It, l9, :0 and 2| may, and preferably are, preheated before being assembled as above described, preferably accurately made contact of the various parts with the adjacent surfaces of the materials b ing formed into the hollow body. Good contact is desirable since this insures the necessary internal support of the materials and avoids their deformation when pressure is applied to the assembly and, moreover, insures that the necessary heat will be transmitted to the inner surfaces of the materials thus thoroughly effecting the required ening of the .Figures 8,

thermo-setting resin thereof.

9, l0 and 11 illustrate various methods of producing the webs between the panels of the hollow body, and except for this difference, the process of producing the hollow bodies is the same as that heretofore described. x

In Figure 8 there is illustrated the use of a wood Figures4to-7. there is h of the sheets 2 auspeo 7 member 20 as the web member, this member having been treated with a heat-hardening phenolic condensation product, or other thermo-setting resin.

In Figures 9, 10 and 11, the webs 2!, II and, respectively, are illustrated as being formed of a plurality of layers of fibrous material disposed in juxtaposed relationship for filling the cavity between the members 20, and 2|. and thus form the web from sheets of fibrous material that contain a thermo-setting resin.

In Figures 12 to 16 inclusive there is illustrated an alternative method of producing a. panel structure in accordance with this invention. In carrying out this method, a plurality of individual tubular channel defining web forming members II are formed from fibrous sheet or. strip material treated or impregnated with an uncured thermo-setting resin. As illustrated, the tubular members 32 are of rectangular shape in crosssection and are conveniently formed by taking 7 a sheet of paper impregnated with an uncured thermo-setting resin, that is previously dried in the paper, and wrapping the sheet a number of times around any appropriate form, such as the internal supporting members or mandrels II, to form a plurality of superposed plies.

The tubular members 32 and the form memhers I I are placed side by side in a metal frame II, similar to that previously described, so that the vertical longitudinal walls of adjacent tubular members 32 abut as shown, for example, at N in Figures and 16. If it is desired to obtain a double thickness of fibrous material at the end of the structure. hand end thereof, a separate strip of fibrous material I! may be used, as shown in Figure 16.

Between the ends of the frame It and the nearest wall of the nearest tubular member 32 one or more additional internal supporting means or cavity-defining members ll may be disposed so as to fill the frame, or, in order that side pressure may be applied to the cavity-defining members such as on the rightand the material therebetween in a direction parallel to the plane of the frame I! and transverse to the length of the cavity-defining members II, the frame may be provided with side pressure exerting devices. Such devices may be of various forms and apparatus fitted with such pressurev devices may be employed in any of the methods of carrying this invention into practice herein described. The means for exerting the said side pressure illustrated in Figure 16 comprises a pressure bar 36 similar in all respects to a cavitydeflning member II, which is adapted to be moved laterally in the direction of the arrows C by means of rotatable spaced screws 31 mounted in the end member ll of the frame I I. the screws 31 being provided with handles 38 or any other suitable means whereby they may be rotated.

Before assembling the tubular members 32 in the frame I! as above explained, fibrous sheets II (to form the bottom sheet 3 of the hollow body) are first arranged upon the bottom cover plate l2. and then the frame II is arranged upon the fibrous sheets H. Now the frame is filled with tubular members I! and the internal supporting means or cavity-defining members ll. Next the top treated fibrous sheets H are placed upon the frame II, the top cover plate 24 is placed in position on the other assembled parts, and the whole assembly is finally placed in the press and subjected to heat and pressure as described in connection with the method illustrated in Figma 4 to 7. The frame it is, of course, divisible to enable the various parts to be removed therefrom after the hardening or curing process has been completed, and to facilitate the removal of the cavity-defining members ll after they have been partially projected from the hollow body. These cavity-defining members may be provided with holes, such as 40, into which a tool may be hooked. This removal of the cavity-defining members may in large scale operations be performed automatically by appropriate hydraulic or other machinery.

It will be readily appreciated that other means of producing the pressure by movement of member I. can be used, such as suitable wedge-shaped members that may be positioned between the member 3! and the end wall 38 of the frame. Also. it will be understood that instead of using tubular members of a rectangular shape, as heretofore described, the tubular members may have any other siutable shape desired, such as the trapezium shape of the tubular members Ii illustrated in Figure 17.

Experiments have shown that very good results can be obtained when making hollow bodies according to the invention by any of the methods already described above, but it is noted that better physical properties are obtained when employing for forming the webs], tubular bodies such as the bodies 32 and ii, for example. above described, or when using web forming bodies of girder cross-section such as will be subsequently described herein. The improved results arise from the fact that when tubular bodies such as 32 or Si or girder section members-as will subsequently be described are employed the top and bottom walls of the tubular members or them: and bottom flanges of the girder-like members form an integral part of the top and bottom sheets 2 of the ultimate hollow body i.

In Figures 18 and 19 there is illustrated a method of forming a hollow body according to this invention by the use of web forming members 52 that have an I or double-T shape in crosssection, these members being prefabricated from ,flbrous' sheet material treated with the required wherein the sheets ll become integral with the lateral portions 53 of the webs 54 while the abutting surfaces or lateral bonding surfaces of the portions 5: become integral with each other. The heat-and-pressure treatment causes a flow of the thermo-setting resin contained in the various members of the assembled parts so that there is an inter-flow of resin between these k members which insures a close bonding of the members. v

One method of producing the web-forming members having the'I or double-T shape in crosssection is illustrated in Figures 21 to 24.

According to this method a sheet or strip 55 of fibrous material of the required dimensions is rolled to constitute a tubular member 58 as seen in end elevation in Figure 21. The rolling is continued until the wall of the tubular member is of the requisite thickness and has the required number of plies. After this tubular member has or at any other stage been made it is deformed from a circular crosssection to the I or double-T cross-section shown in Figure 20, the chain dotted lines 51 in Figure 21 illustrating an intermediate stage in the process of converting the tubular member into the member shown in end view in Figure 20.

As will be seen from Figure 22, each of the flanges 53 of the girder-like member 52, and the web 54, is made up of a plurality of plies or layers of the fibrous sheet which was used to form the tubular member illustrated in Figure 21 and furthermore, the plies of the various parts, i. e. flanges and the web, of the girder-like member 52 are integrally united, all being formed from the same original sheet or strip of fibrous material which at no stage in the prefabrication of the girder-like member 52 is severed at any part.

The fibrous sheet material from which the girder-like members 52 are formed may be treated with a thermo-setting resin material before it is rolled into the form shown in Figure 21 in the formation of the prefabricated girder-like web forming members '52, or these members may be treated with a thermosetting resin subsequently to being formed.

The tubular member 56 is fed in the direction of the arrow E (Figure 23) between a pair of horizontal pressure rollers horizontal axles 59 and Gil disposed directly one above the other and parallel to one another, the distance between the nearest parts of the peripheries of the rollers 51 and 58 being equal to the overall height of the finished girder-shaped web forming element 52. The rollers 51 and 58 thus flatten the tubular member 55 as is clearly illustrated in Figure 23, whilst further pressure rollers 6i and 52 which the tubular member 55 first reaches, and which rotate about parallel vertical axes 63 and 64, are arranged to bear at their peripheries on the sides of the tubular member 56 and press these sides inwardly so as to bring central portions thereof, and equal in depth to the inside depth of the web 54 of the pre-fabricated web forming member 52 shown in Figure 22, together along a central longitudinal medial plane. Thus the tube 56 passes into the apparatus in tubular form and leaves the apparatus, on the opposite side of the rollers 51 and "to that at which it entered the apparatus, in I-shaped girder form.

A modification of the apparatus shown in Figures 22 to 24 inclusive is illustrated in Figures 25 to 2'7 wherein the rollers GI and 52 are replaced with stationary plates 65 and 56 disposed in a common horizontal plane for forcing the tubular member laterally inwardly. The plates 65 and 68 are arranged to provide a flared mouth 69 into which the tube 55 is the hollow body, especially in a hollow body of rectangular shape in plan, preferably, extend in parallelism from one end of the body to the other end and are continuous. Thus the hollow body has parallel open ended channels or cavities extending from end to end thereof, and these channels or cavities may, if desired, be used for housing electric wiring and/or for the air ducts of a ventilating system, or for receiving heat and/or sound insulating material. Naturally a hollow body of this kind, in which the webs run in one direction only, presents higher resistance to bending or deflection in the longitudinal planes containing the webs than it does in a plane at right angles to the lengths of the webs. Therefore, in using such a hollow body in building a structure, the body would preferably be so dis- 51 and 58 arranged on directed. The webs of posed that the webs ran in the direction in which the greater resistance to bending or deflection is required. w

It will, of course, be understood that the hollow bodies may be produced in shapes other than rectangular in plan if desired. For instance, the bodies may be of tapered or truncated sectorlike shape in plan and in such a case the webs would preferably converge to the narrower end of the body instead of being parallel to one another.

If desired, the hollow body may be provided on one or both sides with a facing material of a kind different to the body itself. Such a facing may be provided, for example, for decorative or utilitarian purposes. The facing may for example be a wood veneer, e. g. deal, oak, mahogany or walnut; or it may be a decorative fabric or paper. These specific facing materials are, however, merely mentioned by way of example since almost any fibrous material may be used for the purpose.

The facing material is preferably united to the hollow body by thermo-setting resin simultaneously with the formation of the hollow body itself, and where a relatively hard and wearresisting surface is required on the facing material lt is arranged, in manufacture, that the thermo-setting resin should permeate the whole of the facing material, but where it is desired that the outer surface of the facing material shall retain its normal characteristics (e. g. in the case of a wood facing, where it is desired that the facing should be capable of being glued to another wood surface) then it is arranged that the thermo-setting resin shall not permeate to the outer surface of the facing material.

The treatment of the fibrous material with the thermo-settlng resin may be carried out in any convenient manner, for example by dipping the material in resin in solution, e. g. the resin in alcohol in the case of a spirit-soluble resin or in what is known as a water-solution of the resin if the resin is what is known as a water-soluble" thermo-setting resin. The dipping may be effected by a continuous or intermittent process. The continuous process would be convenient where the fibrous material to be treated was fed from a roll or similar source whilst the intermittent process would be more convenient where the fibrous material was already cut to size in strips or sheets. Instead of impregnating the fibrous material by dipping it in aresin solution, such a solution may be sprayed, painted, or otherwise applied as a coating to the fibrous material either on one side only, or on both sides as required. Where the fibrous material to be treated is, for example, in the form of wood veneers or fibrous sheets which are relatively thick, or where the fibrous material is not very absorbent, or in any other circumstances where it would be advantageous, the treatment of the fibrous material with the thermo-setting resin may be carried out in vacuum.

While the method of manufacture, as well as the article disclosed and described herein illustrate a preferred form of the invention, yet they are subject to alterations without departing from the spirit of the invention, and all modifications that fall within the scope of the appended claims are intended to be included herein.

Having thus fully described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A method of producing a rigid hollow panel cross section; forming members inside by side contact besubstantially parallel groups of superposed uncured thenmo-setting resin impregnated fibrous sheets or laminae so that said web forming members are substantially parallel to one another and have web portions extending transversely of the major surfaces of said groups of sheets 'or laminae at spaced intervals across the widths of said groups of sheets or laminae; (c) temporarily supporting said web forming members internally by supporting means conforming to the shape of the channels defined by the said web forming members; (12) temporarily applying confining means solely to said web forming members and their supporting means to hold them in their assembled positions between the said parallel groups of sheets or laminae; (e) subjecting all of the said plurality of spaced multi-ply web Dortions to pressure exerted transversely of the lengths of such web portions and substantially parallel to the said major surfaces of the said parallel groups of sheets or laminae and also. exerting pressure on the assembly, produced as specified, transversely of said major surfaces of the said parallel groups of resin impregnated sheets or laminae; (f) and, while maintaining pressure on said assembly, applying heat thereto for a predetermined time so as to compress and density all fibrous portions of the assembly inclusive of the said web portions and to bond and harden all such portions into an integral rigid structure; (g) relieving the pressure on said assembly; (h) and removing the said confining means and internal supporting means from the panel so produced.

2. A method of producing a hollow panel structure which includes the steps of (a) winding continuous lengths of uncured thermo-setting resin impregnated paper strip or sheet into a plurality of convolutions to make a plurality of individual multi-ply web forming members of quadrilateral (b) placing said individual Web tween substantially parallel groups of superposed thermo-setting resin impregnated paper sheets or laminae so that said web forming members are substantially parallel to one another and have web portions extending transversely of the major surfaces of said groups of sheets or laminae at spaced intervals across the widths of said groups of sheets or laminae; (c) temporarily supporting said web forming members internally by split metal mandrels conforming to the shape of the channels defined by the said web forming members; (d) temporarily holding said web forming members and said mandrels together so as to prevent relative separation of said web forming members; (e) subjecting all of the said plurality of spaced multi-ply web portions simultaneously to pressure exerted transversely of the lengths of such web portions and substantially parallel to the :said major surfaces of the said parallel groups of sheets or laminae and also exerting pressure transversely of the planes of the said parallel groups of resin impregnated sheets or laminae; (f) and applying heat to the said assembly for a predetermined time so as to compress and densify all fibrous portions of the assembly and to bond and harden all such pori2 tions into an integral rigid structure which is homogeneous to the eye; (a) relieving the pressure on said assembly; (h) and removing the mandrels from the panel so produced.

3. A method of producing a hollow panel structure which comprises, positioning top and bottom sheets in parallel relation upon opposite sides of a plurality of individual web-forming members, said top and bottom sheets comprising a plurality of superposed fibrous sheets in each instance and said web-forming members also comprising a plurality of piles of fibrous material, all of said sheets and plies containing a thermo-set ting resin, said web-forming members having portions extending in planes substantially at right angles to said top and bottom sheets and portions extending laterally from and for the full lengths of the tops and bottoms of said transverse portions and lying closely against the inner surfaces of said top and bottom sheets, the piles of said web-forming members extending continuously from the transverse portions thereof into the laterally-extending portions thereof, said web-forming members extending side-by-side from end to end of the structure with the lateral bounding surfaces of the laterally-extending portions of all the web-forming members closely adjacent to the similar lateral bounding surfaces of the laterally-extending portions of the adjacent web-forming members across the width of the structure, positioning internal supporting means in the passages bounded by the transverse and laterally-extending portions of said web-forming members, retaining the said web forming members and their supporting means against separation from their said positions, applying and maintaining pressure on said web-forming members and interposed supporting means in a direction which is substantially parallel to the planes of the said top and bottom sheets and transverse to the lengths of the transverse portions of said web-forming members to compress the plies of the said transverse portions tightly together, and applying pressure to the assembly in a direction transverse to the planes of the said top and bottom sheets with the application of heat to the assembly, said heat and pressure being sufficient to soften and cause said resin to flow throughout all resin-impregnated fibrous portions of the assembly, to compress and densify all of said fibrous portions and to harden the resin, simultaneously bonding all of said portions of the assembly together into an integral rigid structure which is homogeneous to the eye.

4. A method of producing a hollow panel unit which comprises positioning flexible fibrous laminated bottom sheet material containing a thermo-setting resin upon a supporting plate, placing thereon a frame having removable side portions, positioning in said frame a plurality of web-forming members each comprising portions extending transversely to said bottom sheet material and portions extending laterally from the tops and bottoms of the said transverse portions, said bottom lateral portions resting on the top surface of said bottom sheet material, said web, forming members being fo med of flexible laminated fibrous material containing thermo-setting resin and extending side by side from end to end of said bottom sheet material with the lateral bounding surfaces of the laterally-extending portions of all the web members closely adjacent to the lateral bounding surfaces of the corresponding laterally-extending portions of the adjacent web-forming members across the width of the bottom sheet material so as to. define a plurality of passages between said members, positioning smooth surfaced mandrels in the said passages to support all and laterally-extending web-forming member surfaces, placing flexible laminated fibrous top sheet material containing thermo-setting resin r upon said frame with the bottom surface thereof resting upon the upper laterally-extending portions of said web-forming members. placing a cover plate thereon, applying and maintaining pressure on said web-forming members and mandrels in said frame in a direction which is substantially parallel to the planes of the said bottom sheet material and is transverse to the lengths of the said transverse portions or said web-forming members, to compress the plies of the said transverse web portions tightly together, subjecting the said assembly to pressure transverse to said laminated top and bottom sheet material and applying heat to the whole assembly to soften and then to cause the said resin -to fiow under said pressure through all of the fibrous parts of the assembly and thereby to compress and densify all of the same and simultaneously to bond and harden all parts thereof when the resin sets, into an integral structure which is homogeneous to the eye, releasing the transverse-pressure upon the mandrels and transverse web portions of the structure, thereafter opening said frame, and withdrawing the mandrels lengthwise.

5. A method of producing a hollow panel structure which comprises, positioning flexible fibrous laminated top and bottom sheets in parallel relation upon opposite sides of channel defining laminated web-forming members, the formation of each of said web-forming members including the coiling of fibrous strip material to produce plies which extend continuously throughout the member, all of said sheets and piles containing a thermo-setting resin, said web members having strut portions extending in planes at right angles to said top and bottom sheets and portions extending laterally from the tops and bottoms of said strut portions and lying against the inner surfaces of said top and bottom sheets, said webforming members being arranged so as to extend side-by-side from end to end of the structure with the lateral bounding surfaces of the laterally-extending portions of all the web-forming members closely adjacent to the lateral bounding surfaces of the laterally-extending portions of the adjacent web-forming members across the width of the structure, positioning mandrels in the passages bounded by said web-forming members with a close fit therein, holding the said webforming members in the said arrangement, applying and maintaining pressure on the said web-forming members and mandrels in a direction transverse to the lengths of the said strut portions of said web-forming members and substantially parallel to the planes of top and bottom sheets of the assembly, and applying pressure to the assembly in a direction transverse to the planes of the said top and bottom sheets with simultaneous application of heat to the assembly, said heat and pressure being sufficient to soften and cause said resin to flow throughout all fibrous parts of the assembly, to compress and densify all fibrous portions of the latter and to bond and harden all portions thereof into an integral rigid structure which is homogeneous to the eye, relieving the said top and bottom and the adjacent transverse a and bottom L 14 side pressures, and withdrawing the said man drels from the panel structure produced.

6. A method of producing a rigid unitary hollow panel structure which comprises assembling a lower group of superposed fibrous sheets imregnated with uncured thermo-setting synthetic resin, forming a plurality of individual tubular multi-ply web-forming members of quadrilateral cross-sectional form from fibrous uncured thermo-setting synthetic resin-impregnated flexible material wound into tubular form and enclosing and filled by internal supporting means. placing and retaining a plurality of the said individual tubular web-forming members in parallel side-by-side contacting relationship upon said group of lower sheets, assembling an upper group of superposed fibrous sheets impregnated with the said uncured thermo-setting synthetic resin and placing this group of sheets upon'the upper sides of the web-forming members already placed upon the said lower group of sheets, applying heat and pressure to the said assembly of material to consolidate them and to cause the flow of the said resin throughout all fibrous parts of the assembly and the hardening of the resin with the uniting integrally together of all of the said fibrous-resin-impregnated materials into a unitary whole, said pressure being applied to the said assembled materials in a direction substantially normal to the major planes of said upper and lower groups of sheets and also in a direction transverse to the lengths of the said web-forming members and substantially parallel to the said major planes, relieving the cured structure of pressure. and re moving said internal supporting means from between the webs and the top and bottom sheets of the panel.

'1. A method of producing arigid unitary hollow panel structure which comprises assembling a lower group of superposed fibrous sheets impregnated with uncured thermo-setting synthetic resin, forming a plurality of individual tubular multi-ply web-forming members of quadrilateral cross-sectional form from fibrous uncured thermo-setting synthetic resin-impregnated flexible strip material wound into tubular form, placing a plurality of said individual web-forming members in parallel side-by-side contacting relationship upon said group of lower sheets and with rigid heat-conducting mandrels within said members, assembling a second group of superposed fibrous sheets impregnated with uncured thermo-setting synthetic resin and placing the same upon the upper sides of the said web-forming members which are upon said lower group of sheets, applying side pressure on the said webforming members and enclosed mandrels in a direction transverse to the lengths of the said mandrels to compress tightly together the portions of the piles of the web-forming members that are between the mandrels, and applying top pressure to the assembled parts in a direction transverse to the planes of said groups of sheets, applying heat to the assembly, said heat and pressure being sufilcient to soften and cause said resin to flow throughout all fibrous parts of the assembly, to compress and densify all such parts and to harden and set the resin with the consequent bonding of all of the said fibrous parts into a rigid integral structure, releasing the said pressures and drawing the mandrels endwise from the structure.

8. A method of producing a rigid hollow panel unit which comprises assembling a lower group of superposed fibrous sheets impregnated with uncured thermo-setting synthetic resin, forming a plurality of multi-ply web-forming members oi substantially I-shaped cross-sectional iormby winding uncured fibrous thermo-setting-synthetic-resin-impregnated-fiexible material into members of tubular form and then deiorming said tubular members to an I-shaped cross-sectional form, placing a plurality of said I-shaped webforming members in parallel side-by-side relationship upon said group of lower sheets with the longitudinal edges of the laterally extending flanges of each web-forming members engaging the corresponding edges or the flanges of the next web-forming member or members, filling the passages defined by web-forming members with supporting means for supporting the assembled fibrous-resin materials during a subsequent pressing operation, assembling an upper group of supe llosed fibrous sheets impregnated with the said uncured thermo-setting resin and placing this group of sheets upon the upper flanges of the web-forming members already placed upon the said lower group 01' sheets, applying side pressure to said web-forming members and the supporting means therebetween in a direction transverse to theilengths-oi the said web members and substantially parallel to the majorplanes of the said upper and lower groups of sheets, applying pressure to the-said assembly of materials in a direction substantially perpendicular to the said planes of said groups of sheets and applying heat to the assembly, all to consolidate the fibrous materials thereof andto cause the flow oi the said resin and the'hardening of the latter with the uniting integrally together of all of the said fibrous-resin-impregnated materials into a unitary whole, then relieving the cured structure of pressure, and removing said internal supporting means from between the webs and the top and bottom sheets of the panel.

9. A method of producing a rigid hollow panel structure which comprises, assembling a plurality of superposed pregnated with uncured thermo-setting synthetic resin; forming a plurality of muiti-ply webiorming members each of which has strut-torming portions and lateral extensions at right angles from the tops and bottoms thereof, each or said members being formed from flexible paper strip of the same character as that said superposed sheets and impregnated with like thermo-setting resin, the strip material 01' each or said web-forming members being wound into a plurality of convolutions andarranged to produce plies which extend in a continuous circuit throughout the member, placing a plurality of said web-forming members in parallel side-byside relationship upon said superposed sheets with the strut-forming portions thereof normal to such sheets and with the lower extensions of the web-forming members lying closely upon the uppermost of said sheets and having their longitudinally-extending lateral bounding surfaces engaging with the corresponding surfaces 01' the adjacent members, inserting internal supporting means in the passages formed between said strut-forming portionsand lateral extensions of the web-forming members so as to fill the said passage ing members and their internal supporting means flexible sheets of paper im-.

, retaining the said web-iormin their said side-by-side positions on the said superposed sheets, assembling asecond group of superposed fibrous sheets of like character to said first named sheets and similarly impregnated, positioning this second group of sheets upon the upper extensions of the strut-forming portions of the said web-forming members, applying and maintaining side pressure on the said strut-forming portions and said internal supporting means in adirection transverse to the lengths of said strut-forming portions and substantially parallel to said top and bottom sheets to compress said strut-forming portions between said internal supporting means, and applying heat to the assembly and simultaneously applying top and bottom pressure to the same in a direction normal to said first mentioned direction, said heating and pressing operations being adapted to consolidate the resin-impregnated fibrous materials and to cause the fiow oi the resin through all the said fibrous parts, withv the subsequent hardening of the resin bonding all portions or the fibrous assembly into a rigid integral structure, and thereafter releasing the said pressures and removing thesaid internal supporting means from the structure.

10. A panel structure comprising in combination, a plurality of spaced fibrous laminated sheets arranged substantially parallel to each other, each sheet being impregnated with thermo-setting resin, a plurality oi sp'aced and substantially parallel webs of fibrousmaterial impregnated with thermo-setting resin and interposed betwecn said sheets so as to extend substantially transverse to the major suriaces 01' said sheets, each of said webs forming a portion of a laminated channel defining member composed of fibrous sheet material wound into a plurality of convolutions and bonded to said laminated sheets by the thermo-setting resin in said laminated sheets and in said channel defining members, with the laminae in said webs arranged at an angle to the laminae oi said laminated sheets, said laminated sheets and said webs being compressed in the directions ottheir thicknesses so that said webs form with said laminated sheets a rigid integral densified structural unit.

DESIRE GONDA.

REFERENCES crrEn The. following references are of record in the fileof this patent:

UNITED STATES iwrntrrs 

